The present invention relates to devices for flaw detection of long-distance pipelines, mainly trunk oil pipelines, oil-products pipelines and gas pipelines, by providing acoustic coupling between the ultrasonic transducers and the pipe walls (for example, with the help a fluid plug) and using the method of thickness metering and a so-called “pig” or a scanning device which is put into the pipeline and transported under power of the fluid flow in the pipeline. The scanning pig has built-in transducers, means for measurement, conversion and recording of the measured data and a device for collecting the digital data in the process of pig travel and for processing the obtained data to detect the flaws in the pipe walls and to determine the parameters of the detected flaws, as well as their location in the pipeline.
Known in the art is a device for in-tube flaw detection [RU2018817, RU2042946, RU2108569, U.S. Pat. No. 4,162,635], comprising a body with a built-in equipment for measurement, processing and storage of the measured data, said device including ultrasonic transducers.
When traveling inside the pipeline, this device emits probing pulses and receives the corresponding reflected ultrasonic pulses. The characteristics of the received ultrasonic pulses are used for determining the flaws in the pipeline.
Also known in the art is a device for in-tube flaw detection [U.S. Pat. No. 5,587,534, (relevant patent documents: CA2179902, EP0741866, AU4234596, JP3058352), U.S. Pat. No. 4,964,059, (relevant patent documents: CA1292306, EP0304053, NO304398, JP1050903), U.S. Pat. No. 5,062,300, (relevant patent documents: CA1301299, EP0318387, DE3864497, FR2623626, JP2002923)] comprising a housing incorporating equipment for measurement, processing and storage of the measured data, said equipment comprising a probing pulse generator, an ultrasonic transducer, a pulse processing module, a timer, a processor and a data storage module connected in series.
The device travels inside the pipeline, emits probing pulses towards the pipe wall and receives the respective ultrasonic pulses reflected from the internal and external walls of the pipeline while measuring the transit time of said ultrasonic pulses.
Known in the art is a device for in-tube flaw detection [U.S. Pat. No. 4,909,091, (relevant patent documents: CA1303722, EP0271670, DE3638936, NO302322, JP63221240), U.S. Pat. No. 5,635,645, (relevant patent documents: WO9312420, CA2125565, EP0616692, DE4141123, JP2695702)] comprising a housing incorporating equipment for measurement, processing and storage of the measured data, said equipment comprising a probing pulse generator, an ultrasonic transducer, a pulse processing module, a timer, a processor and a data storage module connected in series.
When traveling inside the pipeline, the device emits probing pulses and receives the respective ultrasonic pulses reflected from the internal and external walls of the pipeline while measuring the transit time of the ultrasonic pulse reflected from the internal wall of the pipeline, the transit time of the ultrasonic pulse reflected from the internal wall, the transit time of the ultrasonic pulse reflected from the external wall. The difference between these values is determined and the obtained data are recorded in the data storage module.
However, the measurement of the pulse transmit time to an external wall of the pipe and back with a given accuracy requires the use of a digital data sharper with a word length greater than in the case of direct measurement of the ultrasonic pulse transit time in a pipe wall (the speed of propagation of ultrasound in a fluid medium is much less than its speed in the pipeline material) This difference is especially significant when metering the thickness of thin-walled pipelines, in which the thickness of the pipe wall can be much less than distance from the transducer to the internal wall of the pipeline.
The measurements with an accuracy sufficient for detection and identification of the flaws and for determination of their parameters requires the use of large-capacity storage devices, whereas the pig moving inside the pipeline has a limited space for data storage devices.
Known in the art is a device for in-tube flaw detection [U.S. Pat. No. 5,460,046, (relevant patent documents: EP0684446, JP7318336)] comprising a housing incorporating equipment for measurement, processing and storage of the measured data, said equipment comprising a probing pulse generator, an ultrasonic transducer, a pulse processing module, a timer, a processor and a data storage module connected in series.
The device travels inside the pipeline, emits probing pulses during its movement and receives the respective ultrasonic pulses reflected from the internal and external walls of the pipeline while measuring the transmit time of the ultrasonic pulse in the pipe wall. The values corresponding to the pipe thickness within permissible limits are neglected, and the values corresponding to the wall thickness outside of the permissible thickness are recorded.
The use of the above device allows one to carry out direct measurement of the time interval between the reception of the ultrasonic pulse reflected from the internal wall of the pipeline and the reception of the ultrasonic pulse reflected from the external wall of the pipeline.
However, the absence of data on the greater part of the length of the monitored pipeline makes it difficult to interpret the data loss, for example, because of poor cleaning of the inner space of the pipeline from paraffin before passing the inspection pig or because of a paraffin deposit on the pipe walls during the travel of the inspection pig through a pipeline filled with heavy oils.
The prototype of the present invention is a device for in-tube ultrasonic thickness metering [U.S. Pat. No. 5,497,661, (relevant patent documents: WO92 10746, CA2098480, EP0561867, DE4040190)], including a housing accommodating equipment for measurements, processing and storage of the measured data, said equipment including a probing pulse generator, an ultrasonic transducer, an amplifier, a comparator with an analog input and with a preset threshold adjusted for recording the ultrasonic pulse reflected from the internal wall of the pipeline, a digital timer, a processor and a data storage module connected in series.
The device is characterized by the presence of an analog-to-digital converter, a buffer memory, and digital data processing modules.
The device travels inside the pipeline, emits probing ultrasonic pulses and receives the corresponding ultrasonic pulses reflected from the internal and external walls of the pipeline. The time interval between the reception of the first ultrasonic pulse reflected from the internal wall of the pipeline and the reception of the second ultrasonic pulse reflected from the external wall of the pipeline are measured. The instants of reception of the first and second ultrasonic pulses are determined, when the electric pulse corresponding to the first or second ultrasonic pulse reaches a threshold value. The electric pulses are digitized by amplitude with a frequency of 28 MHz and resolution of 8 bits. A threshold is set in the analog comparator using the change of state at the comparator output in response to an input signal corresponding to received ultrasonic pulses for starting the operations of quantization of pulses and processing of the obtained digital data. The converted digital data are recorded in a data storage module.
The storage of the information on the shape of the electric pulses or on the amplitudes of the electric signals and instants of time corresponding to these amplitudes in a memory device increases the efficiency of interpretation of the data obtained on the waxed sections of the pipelines characterized by high attenuation of the ultrasonic pulses. However, this also increases the volume of data per given length of the pipeline, which should be stored in the memory device having a limited capacity. As a result, it makes it necessary to decrease the distance to be inspected per pass of the inspection pig.